1. Field of the Invention
This invention relates to a tube coupler of a type for sealing the inner peripheral face of a plug and a valve used for such a tube coupler.
2. Description of the Related Art
The tube couplers of the type are well known which seals the outer peripheral surface of a plug when the plug is connected to a socket. In the tube coupler of this type, the outer peripheral surface of the plug which constitutes a surface to be sealed is liable to be scratched. Japanese Laid-open Utility Model Application Sho 57-110392 discloses a tube coupler in which the inner peripheral face of a plug is made as a face to be sealed, thereby protecting the sealed portion.
In a valve used for closing a fluid passage, the valve head portion and a valve rod portion or a valve tube portion are formed integral with each other, and an O-ring or another seal ring is fitted in an annular groove formed in the valve head portion.
However, the provision of a face to be sealed on the inner peripheral face of the plug, as described above, renders the structure of the socket complicated, thereby increasing the manufacturing cost. On the other hand, in the conventional tube coupler which seals the outer surface of the plug, a groove for receiving a seal ring must be formed in the outer peripheral surface of the plug. The formation of this groove in the plug enhances the machining cost of the plug. Since much more plugs are used than sockets in the field where tube couplers are used, it is uneconomical to used many such plugs. In this respect, it is desired that tube couplers be of an inner-peripheral face sealing type and that both sockets and plugs are manufactured at a low cost.
The width of the above-mentioned annular groove formed in the valve head portion for receiving the O-ring is determined by the dimension of the O-ring provided on the valve. If it happens that the width of the groove becomes wider than that of the O-ring, a perfect sealing effect cannot be expected. Alternatively, if a ring which is not easily deformed, it cannot be fitted in the annular groove in an extended state.